The present invention relates to a planographic printing plate precursor (hereinafter referred to also as a printing precursor) and a printing method employing the precursor.
Recently, as computers or digital technique spread, a computer to plate (CTP) process, in which a printing plate is prepared by directly writing an image onto a planographic printing plate precursor based on an electronic image data, is spreading in a planographic printing plate making process. This process does not require a film-making process, resulting in cost decrease and in simplification of the process.
Synchronized with the spread of CTP processes, office automation in the printing field prevails, and economy of space has been increasingly desired at working environment. A printing press such as True Press produced by Dainippon Screen manufacturing Co., Ltd. or Quick Master 46DI produced by Heiderberg PMT Co., Ltd., comprising an exposure device in it, is compact and does not require an off-line plate setter, which contributes to economy of space.
A planographic printing plate precursor used in these printing presses is in the form of roll and employs a plastic film as a support. The planographic printing plate precursor is transported through a transporting member such as a guide roller, and supplied to a plate cylinder in the printing press, but in many cases the transporting member has had an adverse effect on the printing plate precursor. Typically, the surface of the printing plate precursor is scratched with the transporting member-to produce scratches due to transport, and the scratches have often caused image defects on the printed matter.
Quick master 46DI is a system employing a printing plate material Pearl Dry Plate produced by Prestec Co., Ltd. The Pearl Dry Plate has a structure in that an oleophilic layer, a light-heat converting layer, and a silicone rubber layer are provided in that order on a support, and has problem in that scratches produced on the silicone rubber layer results in contamination on the background (non-image portions).
Further, jamming is likely to occur during transport of the printing plate material. The jamming stops printing, requires the printing plate material to be reset, and further results in great loss of printed matter. In order to reduce jamming due to transport, a method is considered which provides a back coat layer reducing a friction on the rear side of the support opposite the image forming layer. However, this method increases a process for manufacturing a planographic printing plate precursor, resulting in an increase in cost.
Provision of a lubricant-containing layer on the side of the support opposite the image forming layer has problem in that contamination is likely to occur during manufacture.
An object of the present invention is to provide a planographic printing plate precursor which does not produces scratches due to transport nor transport faults, and reduces image defects and cost. Another object of the present invention is to provide a printing method employing the planographic printing plate precursor.